Thiolutin preferentially inhibits RNA synthesis in S. cerevisiae and E. coli. Its effects on nucleotide and nucleic acid synthesis are under investigation and isolation of hypersensitive S. cerevisiae mutants is in progress. We hope to isolate and characterize mutants conditionally defective in RNA synthesis. Investigation of replication of virus-like particles in S. cerevisiae will be attempted, using in vitro systems for translation of associated double-stranded RNA.